Is this too much vibration?

[tvorgitch]

I had a new SS shaft installed with a Lasdrop dripless seal, a split coupler and new cutless bearing. During the pre-purchase survey in 2021, the surveyor noted significant vibration and the cutless bearing was loose, so he suspected the bronze shaft was worn as a new cutless bearing had been recently installed. He recommended replacing the bronze shaft with a SS shaft, which I did early this year.

I was in the yard when the shaft was removed and I could not feel any wear, but the cutless bearing was clearly worn. When the new shaft was installed, I was told that the engine was way out of alignment and they were just able to get it aligned with the existing mounts. I expressed a concern that the alignment was done on the hard and they said it's not an issue.

Once back in the water the vibration appeared to be about the same to me. Due to storms, harbor dredging and a limited crew, I was not able to observe the shaft while underway until yesterday. The yard owner had observed the shaft while motoring at about 5 knots in the harbor and he said he did not see any vibration.

Here is a video of the shaft while motoring at about 2500 RPM and moving about 6.5 knots: https://youtu.be/c3m3mkFhMlY

The first few seconds are at normal speed and then it's in slow motion where the vibration is much more apparent.

For reference, I have a MaxProp propeller.

My suspicion is that the original shaft was not worn but simply way out of alignment which is what caused the rapid wear on the cutless bearing and resulting vibration. Note that this work was done at a different yard.

I'm still happy I upgraded the shaft and seal, but I suspect the alignment is still not correct and I may need new mounts in order to get it properly aligned.
I called Lasdrop and they said they would not recommend disconnecting the coupler in the water, but it was clear that standard disclaimer.

Before I present this video to the yard, I would like some feedback from those of you with more experience. Is this too much vibration and should I insist they re-align the shaft in the water?

Thank you for your help.

[Gregory M]

2nd question: did you "true" split coupler ?
3rd question how old are engine mounts ?

[Jon W]

Accidently deleted my post  so am reposting.

I have an M25XP with a stuffing box. My driveshaft does not have that kind of motion.

My first question would be did you verify the shaft was straight when it was removed? See Gregory's questions above.

How far aft of the strut is the propeller? Did the MaxProp installer verify the spinner lined up with the correct letter for your boat?

[tvorgitch]

I have no idea if the original shaft was straight. They cut it in multiple places during removal.

The new shaft was purchased from Catalina Direct. It was faced with the coupler in the boat yard's machine shop.

I have no idea how far aft the propeller is. They measured the old shaft and sent that information to CD, so I assume it's the "standard distance" if that exists  for a 1993 Catalina 34.

Since the boat seems to perform the same, I suspect that the MaxProp was re-installed correctly.

The tach shows just over 400 hours, but it has a manufacturing date of 2006, so I know it's not the original tach.

I would assume that the engine mounts are the original mounts. The aft starboard engine mount was adjusted to it's maximum height if that is any indication as to the state of the mounts.

[Gregory M]

Based on your description, do yourself a favor, change those engine mounts, period.! You will know that at least eliminated one of of vibration causes.
Proper alignment cannot be done on old stiff/worn-out rubber.

[Noah]

Video definitely shows too much movement. I wouldn't call it vibration. Probably an out-of-alignment issue.  General rule of thumb is to always recheck alignment in the water. I have never seen blue shaft log hose. Interesting, is it silicone?

[Gregory M]

Noah
FYI and others https://ab-marine.com/lasdrop-shaft-seals/

[Ron Hill]

Tom : Something is definitely out of alignment!!  My best guess is that it's the engine to shaft is NOT aligned!! 

As mentioned you might want to look at new engine mounts especially the front port as it's where the oil can drip when changing the filter and soften that mount!!

A few thoughts

[Kyle Ewing]

This article (https://www.yachtsurvey.com/Alignment2.htm) helped me a lot when I was aligning my engine.  The key statement to me is:

The truth is that it is virtually impossible to correctly align engine and shaft with the methods that are commonly used. Because of the rubber mounts, the engine will not be in the same position when running as it is when stopped, when the alignment is made. Propeller thrust and engine torque will cause the engine to change position.

I was able to align my engine so it's as smooth in gear as out.  My approach was to align the coupler as close as possible then run in gear and observe.  I then made minor (half to a full turn at a time) motor mount level adjustments based on observation until it was smooth.  If an adjustment made it worse I reversed it and tried another.  Last time it took over a dozen trips up and down the steps.

It looks to me from the video based on watching the transmission cable that the engine is vibrating mostly left to right with the port side being slightly higher.  Assuming the coupler is aligned, I'd adjust the up/down position of the motor mounts until it's smooth.

[tvorgitch]

Kyle,

Thanks. That article was very informative.

The fact that one mount is at it's upper limit leads me to believe new mounts are in the future. I would normally try and do this myself, but I'm a bit spooked about disconnecting the coupler with the Lasdrop seal and I just paid big $$$ to have all this work done, so I'm taking it back to the yard. The owner is out of town next week and I'm out the following week, so I have a bit of time.

I may just order the mounts myself to have them on hand. It seems the consensus here is to use the Vetus K75's for the M35.

[Breakin Away]

It's OK to do a preliminary alignment in on the hard, but should always finish the job in the water.

..The aft starboard engine mount was adjusted to it's maximum height if that is any indication as to the state of the mounts.

That does not necessarily mean the mount is worn out. But even with brand new mounts, you should never raise the nut more than 3/8" high on the stud, otherwise the mounts will flex horizontally too much. If the motor needs to be higher than 3/8" on the studs, you should put shims under the mounts until you get it under 3/8".

[tvorgitch]

I was able to align my engine so it's as smooth in gear as out.  My approach was to align the coupler as close as possible then run in gear and observe.  I then made minor (half to a full turn at a time) motor mount level adjustments based on observation until it was smooth.  If an adjustment made it worse I reversed it and tried another.  Last time it took over a dozen trips up and down the steps.

Kyle, could you elaborate a bit? Did you do this while tied up? What RPM?

Thanks.

[Kyle Ewing]

I did it while tied up at the dock, perhaps 2000 rpms.  As it got smoother I relied more on feel than sight.  Please be extra careful when the prop is spinning.

[Gregory M]

Another thing to consider: found this on Vetus website under installation instructions,

Flexible engine mounting assembly
It is important that an equal load is applied to the left and the right flexible mounting at the front section of the engine; and the same goes for the
engine's rear section: equal load to the left and the right support. It is admissible - and often unavoidable - that a different load is applied to the front and
rear flexible engine mountings.
A proper adjustment of the engine supports can be assured by the following
procedure:
- Provide for an approximate alignment of engine and shaft assembly, by
means of the nuts on the support spindle, but do NOT connect the propeller shaft yet to the gearbox flange.
- Lift the front part of the engine slightly, up to the point that both front
engine feet become free of the lower nuts of the flexible supports.
- Lower the engine, while adjusting the nuts in such a way that both engine
feet touch the nuts simultaneously.
- Repeat the foregoing with the rear section of the engine.
After the proper adjustment of the flexible engine supports, the precise alignment can be obtained by turning the nuts of the rear and front supports, both
left and right, by exactly the same number of turns.
It is imperative that the flexible engine mountings will be installed free of pretorsion alongships, as this would transmit vibrations and noise to the boat.
The slot in the baseplate of the flexible supports allow for installation corrections sideways.
Verify the proper alignment anew, when the boat has been launched.
For a proper flexible mounting assembly of the ship engine, the following
criteria must be satisfied:
- the rubber engine mountings should be at least pushed in a minimum
amount as a result of the static load *, and
- the rubber engine mountings should be pushed in no more than the
maximum amount as a result of the sum of the static and dynamic load *.
See table and diagram.
* Static load: the load caused by the weight of the engine itself.
Dynamic load: the load caused by the torque of the engine.